The present invention relates to a home diagnostic aid and method for determining the presence of hemoglobin in an aqueous medium, and more particularly, to a diagnostic aid and method for determining the presence of occult blood in fecal matter present in an aqueous medium, and most particularly, to a diagnostic aid and method for determining the presence of occult blood in fecal matter with an easily used and comprehended test procedure that employs a single diagnostic aid in only a single manipulative step and eliminates the necessity of handling the fecal matter prior to or during the test procedure and the handling of the test materials once the test is completed.
Over 100,000 persons in the United States are affected by cancer of the colon and rectum per year, occurring equally in both the male and female. When the number of colorectal cancers occurring each year is combined with the number of cancers occurring in other digestive organs, including the esophagus and stomach, such cancers of the digestive system account for more occurrences of cancer than any other single form of the disease. Contrary to many other forms of cancer, early diagnosis and treatment of digestive tract cancer does result in a cure rate of 80% to 90% of those persons affected by the disease. If, however, the disease is not detected until the later stages, the cure rate can drop drastically to 25% or less. Thus, early detection of the disease is critical to successful treatment of digestive tract cancer.
Most, but not all, cancers of the digestive tract bleed to a certain extent. This blood is deposited on and in fecal matter excreted from the digestive system. The presence of blood in fecal matter is not normally detected, however, until gross bleeding, that is, blood visible to the naked eye, occurs. Most advanced cancers cause gross bleeding.
It is known that digestive tract cancers in the early stages also tend to bleed, giving rise to occult (hidden) blood in the fecal matter. Test equipment and test procedures have been developed for use by physicians in testing for the presence of occult blood in fecal matter. One of the most successful tests is manufactured and sold by Smith Kline Diagnostics of Sunnyvale, California, under the trademark "Hemoccult". The package for the "Hemocult" test is disclosed in U.S. Pat. No. 3,996,006 issued to J. F. Pagano. Briefly, the Pagano test employs an absorbent white paper impregnated with a guaiac reagent and encased in a special test slide having openable flaps on both sides of the test slide. To use the Pagano test slide, one must obtain a sample of fecal matter, smear it onto the guaiac-impregnated paper by opening the panel on one side of the test slide, and thereafter close the panel. A panel on the opposite side of the test slide is then opened and a developing agent, which is a stabilized solution of hydrogen peroxide and denatured alcohol, is applied to the guaiac-impregnated paper. If occult blood is present in the fecal matter smeared on the opposite side of the paper, the product of the guaiac reaction will appear as a blue substance against the white paper background, providing a positive indication of the presence of blood in the fecal matter.
Although the Pagano test is excellent for use by physicians in their offices and by diagnostic laboratories, it is not the type of test that is readily adaptable for use by the ordinary person because of his adverse reaction to handling fecal matter and because of his lack of skill in interpreting the results. As stated above, the Pagano test requires that a specimen of fecal matter be obtained. Normally, a specimen is obtained by procuring a sample on the end of a spatula or a wooden depressor, which is then used to smear the specimen on the paper in the Pagano test slide. Once the sample is obtained and the test procedure completed, both the test slide and the spatula or depressor must be disposed of. Disposal of the used materials can and does present a physical problem to, if not an adverse psychological reaction from, the ordinary person. Thus, the ordinary person is not likely to use the Pagano test because of its unclean nature (at least apparently so to the ordinary person) and because of the disposal problems associated with the used test slide and spatula or depressor. Additionally, the ordinary person does not necessarily have the skill required to analyze, and thus form accurate conclusions from, the test results.
As an alternative, the ordinary person can initiate the Pagano test in his home and then forward the test slide to his physician or a laboratory for addition of the developing agent and analysis of the test. This procedure, however, requires cold storage of the test slide and specimen if there is a significant time lapse before the test can be completed. Certainly, the ordinary person does not wish to store a fecal specimen in his household refrigerator, normally the only cold storage available to him, until he can present the specimen to his physician or an appropriate laboratory. Thus, the general public is not likely to follow or comply with this alternative.
Another test for occult blood is suggested by D. E. Fonner in U.S. Pat. No. 2,838,377. The Fonner test, as disclosed, can be effected in a toilet bowl containing fecal matter. The basic test reagents employed by Fonner are otolidine and benzidine. These reagents in the presence of blood and other reactants produce a dye visible to the naked eye. Although the Fonner test appears to be a solution to the problem of finding a viable home test for occult blood, it has not met with success for two reasons. First, the above-listed reagents are in themselves known to cause cancer and thus are not suitable for general public distribution. Additionally, the Fonner reagents have a relatively high rate of providing false indications of the presence of occult blood.
Thus, to date, the use of the Pagano test, the Fonner test, and other similar tests has been limited primarily to physicians and diagnostic laboratories. Although this limitation might not at first glance present a significant problem, it does limit the early detection of digestive tract cancers, primarily because patients will not see a physician until other symptoms of digestive tract cancers, such as gross bleeding, manifest themselves. Thus, early detection of cancer of the digestive tract still does not occur with the great majority of patients who contract the disease.
Until the advent of the present invention, the most viable method for testing for occult blood in the home is that disclosed by W. G. Friend in U.S. Pat. No. 4,175,923, assigned to Hematec Corporation of Bellevue, Wash. The Friend test again uses the reliable and time-proven test reagent guaiac. In accordance with the preferred embodiment disclosed by Friend, guaiac is impregnated on an absorbent substrate such as an absorbent laboratory filter paper. A developing solution, comprising an alcohol and peroxide, is applied to the guaiac-containing absorbent substrate. The activated test substrate is then deposited in a toilet bowl, for example, containing feces. If occult blood is present, the guaiac is oxidized to a blue dye that is visible against the absorbent substrate.
While the Friend test overcomes some of the drawbacks of the Pagano test and the Fonner test, the Friend test still has its disadvantages. First, the alcohol-guaiac solution is highly flammable, presenting a potential hazard to a user in the bathroom, a common smoking area. Secondly, the addition of the solution to the test substrate in both the Pagano and Friend tests will almost always leave a brown or blue green ring on the substrate unless the solution is evenly distributed over the entire substrate. This ring can easily be misinterpreted by the inexperienced person as a positive test result. As a consequence, it is desirable to eliminate these problems.